Hi!
Database.changeVersion expects oldVersion and newVersion arguments. The
Database also specifies a version attribute.
The transaction steps tell to fail the transaction due to the failed
preflight condition if oldVersion does not match the current database
version.
Meanwhile, the callbacks have been made optional, and rightly so.
So:
- if the author does not use the callbacks, there no error reporting that
the preflight condition failed
- the version check can be done synchronously when changeVersion is
called because the Database object has immediate access to that value, and
it's much more convenient for the author to just get an exception (like
INVALID_STATE_ERR) than to have to go through the entire callback process
just to realize later that the transaction failed due to the mismatched
version. It also spares the user agent from creating and executing a
transaction that WILL fail.
To solve these issues, I would suggest doing immediate synchronous
validation of the version when changeVersion is called, throwing an
exception on error, and drop that step from the preflight operations.
Thank you.